Mechanism for producing minute movement of a head of a disk device

ABSTRACT

A mechanism for producing a minute movement of a head of a disk device, which simplifies wiring in a head actuator and reduces the cost of the device by decreasing the distance between adjacent carriage arms for putting a recording medium therebetween. The mechanism for producing a minute movement of the head is placed between the base portion of a head suspension and the leading end portion of each of the carriage arms of a rocking type head actuator. This mechanism consists of an actuator base fixed at the end portion of a carriage arm, a hinge plate attached to the base portion of a head suspension, and shearing type piezoelectric elements interposed between opposite surfaces of an actuator base and the hinge plate. A step portion is provided at an end portion of the actuator base. The piezoelectric elements are placed in a portion corresponding to the thickness of the carriage arm. This prevents the sum of the thicknesses of the actuator base and the piezoelectric elements from exceeding the height of the top surface of the carriage arm. Consequently, the height of the head actuator is reduced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a mechanism for producingminute movement of a head of a disk device and, more particularly, to amechanism for causing a minute movement of a head of a disk device inthe vicinity of a leading end of a piezoelectric element by utilizingshear deformation of the piezoelectric element.

2. Description of the Related Art

In recent years, the processing precision of information devices hasadvanced. Thus, there is a demand for actuators required to controlmicro-distance movement of constituent components of the informationdevices. That is, actuators capable of controlling micro-distancemovement of a head or the like are needed in the fields of, for example,devices for correction of focal points of optical systems and control oftilt angles of optical components thereof, printing devices forprinters, and head actuators of magnetic disk devices.

Among such information devices, a magnetic disk device a primarymultimedia device, the scale of the market of which has sharplyincreased. Multimedia devices deal with mass image and audio data athigh speeds. Thus, there is a need for development of a device havinghigher storage capacity. Generally, a magnetic disk mass storage devicerealized by increasing the storage capacity per disk.

However, it is indispensable for realizing a magnetic disk medium havinga high recording density to increase the number of tracks per inch(TPI), that is, to reduce the width of each track. Further, when thestorage density of a magnetic disk is significantly increased, the trackpitch abruptly decreases. Thus, there is a technical problem as to howthe positioning of a head element for reading data from and writing datato a recording track is accurately performed. Hence, there has been putto practical use a head actuator, which is caused by a motor called a“VCM” to perform a rocking motion and has a mechanism capable of causingminute movement of a head independently of a driving operation by theVCM. This mechanism for producing a minute movement of a head must beminiaturized.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide a mechanism forproducing a minute movement of a head, which is suitable for accessingdisks in a narrow space between stacked disks, in a head actuator of amagnetic disk unit having such a mechanism.

A second object of the present invention is to reduce the cost of a diskdevice by simplifying the wiring for driving a mechanism for producing aminute movement of a head and wiring for connecting a head suspension tothe ground.

To achieve the foregoing objects, according to an aspect of the presentinvention, there is provided a mechanism (hereunder sometimes referredto as a first mechanism of the present invention) for producing a minutemovement of a head, provided between a base portion of a head suspensionhaving the head at an end portion thereof and an end portion of acarriage arm swinging around a rotation shaft in a rocking type headactuator. This mechanism comprises a stationary member, which is fixedto the end portion of the carriage arm, a moving member, which isattached to the base portion of the head suspension, and a displacingmember, which is interposed between a free-end-side predetermined-areasurface of the stationary member and a free-end-side predetermined-areasurface of the moving member opposed to the stationary member, having atop surface to be displaced with respect to a bottom surface thereof byapplying a voltage in a direction of the thickness thereof. Thisdisplacing member is placed at a side opposite to a recording medium tobe accessed, with respect to an attaching surface of the stationarymember, which is attached to the end portion of the carriage arm, and anattaching surface of the moving member, to which the base portion of thehead suspension is attached.

In the first mechanism of the present invention, a space formed betweenthe free-end-side predetermined-area surface of the stationary memberand the free-end-side predetermined-area surface of the moving member byfolding a part adjoining the attaching surface of the stationary member,which is attached to the end portion of the carriage arm, like a crank,to a side of the recording medium. The displacing member is accommodatedin this space.

Further, in the first mechanism of the present invention, a space formedbetween the free-end-side predetermined-area surface of the stationarymember and the free-end-side predetermined-area surface of the movingmember by folding a part adjoining the attaching surface of the movingmember, which is attached to the end portion of the carriage arm, like acrank, to a side of the recording medium. The displacing member isaccommodated in this space.

Furthermore, the first mechanism of the present invention has thefollowing characteristic features:

(1) Application of the voltage to the displacing member is performed bysheet-like electrode members provided on the top and bottom surfaces ofthe displacing member. Moreover, insulating members are interposedbetween the electrode member and the stationary member and between theelectrode member and the moving member. Each of the electrode membershas a connecting terminal portion connected to a lead wire that isconnected to a power supply.

(2) The carriage arm is connected to the ground. The stationary memberis constituted by an electrical conductor and fixed to the end portionof the carriage arm in such a manner as to electrically conduct. Aninsulating layer, a conductive layer, and an electrode member having aconnecting terminal portion connected to a lead wire, which is connectedto a power supply, are provided between the stationary member and thedisplacing member so that the conductive layer is provided at the sideof the displacing member. The moving member is constituted by anelectrical conductor and is attached to the base portion of the headsuspension in such a way as to electrically conduct. The moving memberis connected to the stationary member by an electrical conductor.

(3) The carriage arm is connected to the ground. The stationary memberis constituted by an electrical conductor and fixed to the end portionof the carriage arm in such a manner as to electrically conduct. Aninsulating layer, a conductive layer, and an electrode member having aconnecting terminal portion connected to a lead wire that is connectedto a power supply, are provided between the stationary member and thedisplacing member so that the conductive layer is provided at the sideof the displacing member. The moving member is constituted by anelectrical conductor and is attached to the base portion of the headsuspension in such a way as to electrically conduct, and is overlaiddirectly on the displacing member. The moving member is connected to thestationary member by an electrical conductor.

The conductor is also used as a part of the head suspension.

(4) The moving member is constituted by an electrical conductor. Anelectrode member consisting of an insulating layer and an electricalconductive layer is fixed to a base-portion-side part of a surface ofthe moving member, which is opposite to the displacing member. Theelectrode member has a wire connecting portion connected to externalwiring. The conductive layer of the electrode member is connected to themoving member by an electrical conductor. The electrical conductor canbe a conductive adhesive agent.

(5) The carriage arm is connected to the ground. An electrode memberconsisting of an insulating layer, an electrical conductive layer, and aconnecting terminal portion to be connected to an external lead wire isprovided so that the conductive layer is in contact with amoving-member-side surface of the displacing member. Astationary-member-side surface of the displacing member is electricallyconnected to the carriage arm through the stationary member constitutedby an electrical conductor. The moving member, to which the headsuspension is attached, is constituted by an electrical conductor andconnected to the stationary member by an electrical conductor.

(6) The carriage arm is connected to the ground. An electrode memberconsisting of an insulating layer, an electrical conductive layer, and aconnecting terminal portion to be connected to an external lead wire isprovided so that the conductive layer is in contact with amoving-member-side surface of the displacing member. Astationary-member-side surface of the displacing member is electricallyconnected to the carriage arm through the stationary member constitutedby an electrical conductor. The moving member is constituted by anelectrical conductor, is connected to the base portion of the headsuspension in such a way as to electrically conduct, and is overlaiddirectly on the displacing member. The head suspension is connected tothe stationary member by an electrical conductor.

Further, the mechanism of the configurations (1) to (6) may have thefollowing characteristic features:

(7) The electrode member is constituted by stacking a stainless-steelthin plate, a polyimide layer, and a copper foil in this order.

(8) The electrode member is constituted by a flexible printed circuitboard. The connection of the printed circuit board, the piezoelectricelement, the moving member, and the stationary member is performed bygluing.

(9) The wire connecting portion of the electrode member is folded insuch a way as to fit along a side surface of the carriage arm.

(10) The moving member has a hinge portion for increasing a moving rangeof the head suspension. Moreover, the electrode member has a notchformed in accordance with a shape of a hinge of the moving member havingthe hinge.

Incidentally, in any of the mechanisms of the aforementionedconfigurations, a surface, on which the moving member is mounted, of thehead suspension can be flush with an outer surface of the stationarymember opposite to an inner surface which is mounted on the carriagearm.

Further, to achieve the foregoing objects, according to another aspectof the present invention, there is provided a mechanism for producing aminute movement of a head, which is provided between a base portion of ahead suspension having a head at an end portion thereof and an endportion of a carriage arm adapted to swing around a rotation shaft in arocking type head actuator. This mechanism comprises a stationary memberfixed at an end portion of the carriage arm, a moving member attached tothe head suspension, a displacing member which is interposed between apredetermined free-end-side region surface of the stationary member anda predetermined free-end-side region surface of the moving memberopposed to this stationary member and has a top surface adapted to bedisplaced with respect to a bottom surface thereof by applying a voltagein the direction of thickness thereof, and a sheet-like electrode memberwhich is disposed on at least one of top and bottom surfaces of thisdisplacing member and which consists of an insulating layer andconductive layers. The electrode member has a wire connecting portionconnected to external wiring. This wire connecting portion is foldedalong a side surface of the carriage arm.

According to the present invention, in a head actuator of a magneticdisk device, a mechanism for producing a minute movement of the head canhave a structure suitable for accessing disks mounted at smallintervals. Moreover, the cost of the disk device can be reduced bysimplifying the wiring for driving the mechanism for producing a minutemovement of the head, and the wiring for connecting the head suspensionto the ground.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, objects and advantages of the present invention willbecome apparent from the following description of preferred embodimentswith reference to the drawings in which like reference charactersdesignate like or corresponding parts throughout several views, and inwhich:

FIG. 1 is an assembly perspective diagram showing the constitution of aconventional mechanism for producing a minute movement of a head;

FIG. 2 is an assembly perspective diagram showing the practicalconstitution of the conventional mechanism for producing a minutemovement of a head;

FIG. 3A is a perspective diagram showing a wiring structure of theconventional mechanism for producing a minute movement of a head;

FIG. 3B is a plan diagram showing a base of FIG. 3A;

FIG. 4A is a left-hand side view of a head actuator having a mechanismfor producing a minute movement of a head according to the presentinvention;

FIG. 4B is a plan view of the head actuator having the mechanism forproducing a minute movement of the head according to the presentinvention;

FIG. 4C is a right-hand side view of a head actuator having themechanism for producing a minute movement of the head according to thepresent invention;

FIG. 5A is a diagram schematically showing a first mode of a mechanismfor producing a minute movement of a head according to the presentinvention;

FIG. 5B is a diagram schematically showing a second mode of a mechanismfor producing a minute movement of a head according to the presentinvention;

FIG. 6 is a side view showing the constitution of a first embodiment ofthe present invention;

FIG. 7A is an assembling perspective diagram showing the practicalconstitution of the first embodiment of the present invention;

FIG. 7B is a perspective diagram showing a condition of a secondelectrode before processed;

FIG. 8A is a side view showing the first embodiment shown in FIG. 7Aafter assembled;

FIG. 8B is a plan view of the first embodiment shown in FIG. 8A;

FIG. 8C is a plan view of a modification of the embodiment shown in FIG.8B;

FIG. 9A is a developed view of an electrode member into which first andsecond electrode members are integrated with each other;

FIG. 9B is a perspective diagram showing a shape of the electrode memberof FIG. 9A after it is assembled;

FIG. 9C is a perspective view of a modification of the electrode memberof FIG. 9B;

FIG. 9D is a perspective diagram showing the electrode members composedof the electrode member of FIG. 9B and formed separately from eachother;

FIG. 9E is a perspective diagram showing the electrode members composedof the electrode member of FIG. 9C and formed separately from eachother;

FIG. 10A is an assembly perspective diagram showing the practicalconstitution of a second embodiment of the present invention;

FIG. 10B is a plan view showing the second embodiment of FIG. 10A afterassembled;

FIG. 10C is a side view of the second embodiment of FIG. 10B;

FIG. 11A is an assembly perspective diagram showing the practicalconstitution of a modification of the second embodiment of the presentinvention;

FIG. 11B is a plan view showing the modification of FIG. 11A afterassembled;

FIG. 12A is an assembly perspective diagram showing the practicalconstitution of another modification of the second embodiment of thepresent invention;

FIGS. 12B and 12C are partly enlarged sectional views of examples of theelectrical connection between a third electrode member and a hinge plateshown in FIG. 12A;

FIG. 13A is an assembly perspective diagram showing the practicalconstitution of a third embodiment of the present invention;

FIG. 13B is a plan view of the assembled third embodiment of FIG. 13A;

FIG. 13C is a side view of the third embodiment of FIG. 13B;

FIG. 14A is an assembly perspective diagram showing the practicalconstitution of a modification of the third embodiment of the presentinvention;

FIG. 14B is a plan view showing the modification of FIG. 14A after it isassembled;

FIG. 14C is a side view of the modification of FIG. 14B;

FIG. 15A is an assembling perspective diagram showing the practicalconstitution of a fourth embodiment of the present invention;

FIG. 15B is a perspective diagram showing the fourth embodiment after ahead suspension and a hinge plate are assembled;

FIG. 16 is a side view showing the constitution of a fifth embodiment ofthe present invention;

FIG. 17 is an assembly perspective diagram showing the practicalconstitution of the fifth embodiment of the present invention;

FIG. 18A is a side view showing the fifth embodiment of FIG. 17 afterassembled;

FIG. 18B is a plan view of the fifth embodiment of FIG. 18A;

FIG. 18C is a plan view of a modification of the embodiment of FIG. 18B;

FIG. 19A is an assembly perspective diagram showing the practicalconstitution of a sixth embodiment of the present invention;

FIG. 19B is an assembly perspective diagram showing the practicalconstitution of a modification of the sixth embodiment of the presentinvention;

FIG. 20 is an assembly perspective diagram showing the practicalconstitution of another modification of the sixth embodiment of thepresent invention;

FIG. 21A is an assembly perspective diagram showing the practicalconstitution of a seventh embodiment of the present invention;

FIG. 21B is an assembly perspective diagram showing the practicalconstitution of a modification of the seventh embodiment of the presentinvention;

FIGS. 22A and 22B are diagrams respectively illustrating, forcomparison, a change in the height between a carriage arm and a sliderof a conventional mechanism for producing a minute movement of a head,and a change in the height between such elements of a mechanism forproducing a minute movement of a head according to the presentinvention; and

FIG. 23 is an assembling diagram showing the practical constitution ofan eighth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing the preferred embodiments of the present invention, anexplanation will be given of a conventional mechanism for producing aminute movement of a head of a disk device, which is shown in FIGS. 1 to3B.

FIG. 1 illustrates the essential constitution of a head actuator 80 of adisk device provided with a mechanism 70 which has been already proposed(in the Japanese Patent Laid-Open No. 11-31368 Official Gazette) andused for producing a minute movement of a head. In FIG. 1, referencenumeral 72 designates a carriage arm of the head actuator 80. A baseportion of a head suspension portion 74 having a leading end part, towhich a head slider 71 is attached, is mounted onto a leading endportion of this carriage arm 72 through the mechanism 70. The mechanism70 consists.of shearing-type piezoelectric elements 31 and a movingmember 40. The base portion of the head suspension 74 is attached to anend of the moving member 40. Further, when a voltage is applied in adirection of thickness of the piezoelectric element 31, thepiezoelectric elements 31 undergo shear deformation. Thus, the movingmember 40 is displaced, so that the head slider 71 provided at the endportion of the head suspension 74 is minutely displaced.

The moving member 40 actually has a movement-amount increasing mechanismfor increasing the movement-amount of the head suspension 74. FIG. 2shows this example. In the case of this example, two piezoelectricelements 31 of the shearing type are attached onto the carriage arm 72.Two arrows described by dashed lines on the piezoelectric elements 31indicate the directions of polarization thereof, which are perpendicularto the direction of thickness of the piezoelectric elements 31 andopposite to each other. An electrode 21 and wiring patterns 22 and 23for applying a voltage to the piezoelectric elements 31 are provided onthe carriage arm 72.

In the moving member 40 mounted on the two piezoelectric elements 31, afirst notch 41 serving as the movement-amount increasing mechanism isprovided corresponding to the position of a space between the twopiezoelectric elements 31. Also, second notches 42 serving as themovement-amount increasing mechanism are respectively formed from bothside ends of the moving member 40 in directions perpendicular to thefirst notch 42. A hinge 45 is formed at a portion at which the firstnotch 41 intersects with each of the second notches 42. Further, aleading-end-side portion of the moving member 40 partitioned by thesecond notch 42 acts as a movement-amount increasing portion 44. Thebase portion of the head suspension 74 having the head slider 71 at theleading end portion thereof is attached to this movement-amountincreasing portion 44. A stationary member 40 serves as one of theelectrodes of the piezoelectric elements 31. A part of the stationarymember 40 is connected to the wiring pattern 23 by a lead wire 37 so asto apply an electric potential to the stationary member 40.

In the case of the mechanism 70 for producing a minute movement of ahead in this example, the head slider 71 can be displaced in thedirections of arrows U and UC by applying a voltage between theelectrode 21 and the moving member 40.

However the mechanism for producing a minute movement of a head, whichis disclosed by the Japanese Patent Laid-Open No. 11-31368 OfficialGazette, has a three-layer structure in which the piezoelectric elements31 are mounted on the electrode 21 of the carriage arm (or head arm) 72,and in which the head suspension (or spring arm) 74 is mounted on thepiezoelectric elements 31 through the moving member 40. As compared witha thickness of only a head mounting block of another conventionalmechanism, the thickness of the mechanism for producing a minutemovement of a head disclosed in the aforementioned Official Gazette isincreased by a thickness of a part from the carriage arm 72 to the headsuspension 74. Thus, the mechanism disclosed in the aforementionedOfficial Gazette has a drawback in that the structure of this mechanismis not suitable for reducing the thickness of the head actuator 80.Furthermore, such an increase in the thickness of the mechanism resultsin an increase in the interval between the adjacent disks. Thus, thenumber of disks, which can be mounted in the disk device, is reduced.Consequently, this mechanism has another drawback in that the storagecapacity of a disk unit employing this mechanism is less than that ofanother conventional disk device, which is of the same height as thedisk unit.

Further, the head suspension of the magnetic disk device should beelectrically connected to the ground so as to reduce the noise caused ona recording signal inputted to and a reproducing signal outputted fromthe head. In an ordinary head actuator having no mechanism for producinga minute movement of a head, usually, a carriage arm is connected to theground. Thus, a head suspension caulked to this carriage arm is alsoconnected to the ground. However, a head actuator, into which amechanism for producing a minute movement of a head is incorporated, hasa structure in which piezoelectric elements are inserted between acarriage arm and a head suspension. This head actuator, therefore,requires a line for connecting the head suspension to the ground, and aline for driving the piezoelectric actuators.

However, in the case of the mechanism for producing a minute movement ofa head which is described in the Japanese Patent Laid-Open No. 11-31368Official Gazette, the piezoelectric elements 31 are sandwiched betweenthe carriage arm 72 and the moving member (or hinge plate) 40. It is,thus, difficult to draw out the wire from the electrode. Moreover,stainless steel (SUS) materials are used as the materials of thecarriage arm 72 and the moving member 40. Thus, the connectivity of asolder connection of a copper wire to each of such composing elements isextremely low. This makes it more difficult to route the aforementionedwires.

On the other hand, it is considered that a relay flexible printedcircuit board (namely, a relay FPC) 24 is folded and connected directlyto the moving member 40, as illustrated in FIG. 3A (namely, FIG. 17described in the Japanese Patent Laid-Open No. 11-31368). However, anoperation of connecting the relay FPC 24 thereto is performed after thepiezoelectric elements 31 and the moving member 40 are attached to thecarriage arm 20. It is, thus, difficult to secure a space for attachingthe folded relay FPC 24 thereto. Therefore, the operation of attachingthe relay FPC 24 thereto is troublesome and difficult to perform.

Hereinafter, the methods of implementing the mechanism 10 for producinga minute movement of a head according to the present invention will bedescribed in detail based on practical embodiments thereof.Incidentally, in the figures, each of constituent members of themechanism 10 of the present invention, which is the same as thecorresponding constituent member of the conventional mechanism describedby referring to FIGS. 1 to 3B, will be described by being designated bythe same reference character as denoting the latter correspondingconstituent element of the conventional mechanism.

FIGS. 4A to 4C show the constitution of a head actuator 60, which hasthe mechanism 10 for producing a minute movement of a head according tothe present invention, in a disk device. FIGS. 4A, 4B, and 4C are aleft-hand side view, a plan view, and a right-hand side view of the headactuator 60. This head actuator 60 is mounted on a rotation shaft 76 ofa pin and swings around this rotation shaft 76. The carriage arm 72formed in such a way as to be like a comb when seen from a side thereofis provided at the other side of the rotation shaft 76. One or two headsuspensions 74 are attached to a tip end of each carriage arm 72. A headslider 71 having a head for transferring data to and from a disk mediumis provided at a tip end of the head suspension 74.

Two support arms 73 are provided at the other-side end of the rotationshaft 76. A flat coil 75 is supported between the support arms 73. Theflat coil 75 is provided in such a way as to be opposite to a magneticcircuit (not shown) provided at a base-side portion of the disk device.The head actuator 60 swings according to a value of the level ofelectric current fed to the flat coil 751. The mechanism 10 forproducing a minute movement of the head is provided between the headsuspension 74 and the carriage arm 72 of each set and is operative tocause a minute movement of the head suspension 74 independent of aswinging motion of the head actuator 60.

FIGS. 5A and 5B show the essential constitution of the mechanism 10 forproducing a minute movement of the head as two modes of embodimentswhich can be obtained by practicing the present invention. Basically,the mechanism 10 for producing a minute movement of the head accordingto the present invention consists of an actuator base 30 serving as astationary member fixed at a tip end portion of the carriage arm 72, ahinge plate 40 serving as a moving member attached to the base portionof the head suspension 74, and a piezoelectric element 31 serving as adisplacing member interposed between the actuator base 30 and the hingeplate 40. Shearing type piezoelectric devices, whose top surfaces aredisplaced with respect to the bottom surfaces thereof by applying avoltage thereto in a direction of thickness thereof, are used as thepiezoelectric elements 31. In this embodiment, electrodes 1 and 2 areprovided on the top and bottom surfaces of the piezoelectric element 31,respectively, so as to apply a voltage to the piezoelectric element 31in the direction of thickness thereof. The actuator base 30 or the hingeplate 40 may be constituted by an electrical conductor and used insteadof one of the electrodes 1 and 2.

In the mechanism of the present invention, the piezoelectric element 31is placed at a side opposite to the slider 71 with respect to anattaching surface, which is connected to a tip end portion of thecarriage arm 72, of the actuator base 38. Moreover, the piezoelectricelement 31 is placed at the side opposite to the slider 71 with respectto an attaching surface, which is connected to the base portion of thehead suspension 74., of the hinge plate 40. This is because a dead spacedue to the thickness of the carriage arm 72 is utilized for constitutingthe mechanism 10 for producing a minute movement of the head, owing tothe fact that the thickness of the carriage arm 72 is much greater thanthe thickness of each of the actuator base 30 and the hinge plate 40.

There are considered two modes, namely, first and second modes ofconstituting the mechanism 10 at such a place. In the first mode, such aspace provided between the plate-like hinge plate 40 and the actuatorbase 30 by folding the actuator base 30 like a crank in a direction inwhich the actuator base 30 thus becomes further away from the slider 71,as illustrated in FIG. 5A. In the second mode, such a space is providedbetween the plate-like actuator base 30 and a hinge plate 50 by foldingthe hinge plate 50 against the plate-like actuator base 20 like a crankin a direction in which the hinge plate 50 becomes further away from theslider 71, as illustrated in FIG. 5B. Hereunder, the mechanisms forproducing a minute movement of a head, which are respectivelyconstituted in the first and second modes, will be described by beingdesignated by the same reference character 10.

Thus, first, the mechanisms of the present invention for producing aminute movement of the head, which are constituted in the first mode,will be described here in below, based on first to fourth embodimentsthereof.

FIG. 6 shows the constitution of the mechanism 10 for producing a minutemovement of a head, which is the first embodiment of the presentinvention. In the first embodiment, a stationary portion 33 of theactuator base 30 is fixed to the carriage arm 72 by a caulkingprojection 32. The carriage arm 72 is usually connected to the ground.An end portion 35 of the actuator base 30 is folded twice like a crank.Further, a step or ramp portion 34 is formed between the stationaryportion 33 and the end portion 35. The end portion 35 is folded in sucha manner as to be in parallel with the stationary portion 33. Thepiezoelectric elements 31 sandwiched between the first electrode 1 andthe second electrode 2 are mounted on the end portion 35 of the actuatorbase 30.

Each of the first electrode 1 and the second electrode 2 consists of aconductive layer 11 constituted by an electrical conductor, such ascopper, an insulating layer 12 constituted by an electrical insulator,such as polyimide, and a conductive layer 13 constituted by anelectrical conductor, such as stainless steel, which are stacked fromthe side of the piezoelectric elements 31 in this order. The use of acopper layer as the conductive layer 11 facilitates solder connectionbetween this layer and a relay wire (to be described later). This makesthe assembly work of this mechanism easier and contributes to a reducedcost thereof. Moreover, the polyimide layer and the copper layer can beformed thinner, by thin film deposition. This enables reduction inthickness of the electrodes, and contributes to a reduced thickness of apiezoelectric actuator. Furthermore, the base portion of the headsuspension 74 is fixed onto this second electrode 2 through the hingeplate 40. Incidentally, these two layers, namely, the conductive layer11 and the insulating layer 12 may be used as the electrodes 1 and 2.Further, instead of the SUS material, polyimide, and copper layermaterials, materials equivalent thereto, for instance an FPC, may beused as the materials of these layers.

During assembly, the top surfaces of the actuator base 30 and the hingeplate 40 are trued up and made to be flush with each other by settingthe height of the step portion 34 of the actuator base 30 at apredetermined height. Thus, when the top surfaces of the actuator base30 and the hinge plate 40 are trued up and flush with each other, thehinge plate 40 can be easily connected to the ground by connecting theactuator base 30 and the hinge plate 40, which are to be connected tothe ground, through an electrical conductor.

FIG. 7A, shows the practical constitution of the first embodiment of thepresent invention. The stationary portion 33 of the actuator base 30 isinserted, using a caulking projection 32, into a caulking hole 72 abored in the carriage arm 72, and then caulked and fixed thereto. Thecarriage arm 72 is connected to the ground. The end portion 35 of theactuator base 30 is made by the step portion 34 to be lower than thestationary portion 33 by a height of one step or ramp. The piezoelectricelements 31 put between the first electrode 1 and the second electrode 2are mounted on the end portion 35. Each of the first electrode 1 and thesecond electrode 2 has the three-layer structure described by referringto FIG. 6. Each of the conductive layers 11 is placed at a side that isin contact with the piezoelectric elements 31.

A wire connecting portion 14 projecting from the end portion 35 to aside thereof is provided in the first electrode 1. This wire connectingportion 14 is folded at a right angle toward a side in such a way as tobe away from the piezoelectric elements 31 and to be in parallel with aside surface of the carriage arm 72 after the piezoelectric elements 31are mounted on the end portion 35. The conductive layer 11 of the firstelectrode 1l is provided at the side, which is in contact with thepiezoelectric elements 31, and thus directed outwardly with the wireconnecting portion 14 folded as described above.

On the other hand, a wire connecting portion 25 is provided in thesecond electrode 2. This wire connecting portion 25 is constituted insuch a way as to be adjacent to the wire connecting portion 14 of thefirst electrode 1 when folded. Thus, the wire connecting portion 25 ofthe second electrode 2 is provided in such a manner as to protrude fromthe second electrode 2 to the side of the carriage arm 72, asillustrated in FIG. 7B. Further, the wire connecting portion 25 and thesecond electrode 2 are connected an ear portion 25 a slightly protrudingsideways from the end portion 35 of the actuator base 30. This wireconnecting portion 25 is made parallel with a side surface of thecarriage arm 72, while the conductive layer 11 of the second electrode 2is exposed to the outside as illustrated in FIG. 7A, by folding a borderportion, which is indicated by a dotted line, between the ear portion 25a and the second electrode 2 at a right angle so that the portion 25 isa valley portion.

The piezoelectric elements 31 between the first electrode 1 and secondelectrode 2 are the same as the elements 31 described with reference toFIG. 2. The directions of polarization of the piezoelectric elements 31are perpendicular to the direction of thickness of these element's andare opposite to each other. Moreover, the hinge plate 40 mounted on thepiezoelectric elements 31 is the same as the element 40 described withreference to FIG. 2, and has base portions 43 and a movement-amountincreasing portion 44 partitioned by a first notch 41 and second notches42. Furthermore, the base portions 43 of the hinge plate 40 are mountedon the second electrode 2. The head suspension 74 is fixed to themovement-amount increasing portion 44 of the hinge plate 40 by spotwelding. Incidentally, reference numeral 77 denotes a relay-FPCattaching portion provided in a base-portion-side surface of the headsuspension 74.

FIG. 8A is a side diagram showing the mechanism 10 for producing aminute movement of a head, which is the first embodiment of the presentinvention illustrated in FIG. 7A, after it is assembled. FIG. 8B is aplan view of the assembled mechanism 10 for producing a minute movementof the head. When the mechanism 10 for producing a minute movement ofthe head is assembled, the first wire connecting portion 14 and thesecond wire connecting portion 25 respectively provided on the bottomand top surfaces of the piezoelectric elements 31 are placed in such away as to be adjacent to each other. This facilitates soldering of therelay FPC in which lead patterns for the wire connecting portions 14 and25 are formed. Consequently, the applying of a voltage to each of thefirst electrode 1 and the second electrode 2 is easily achieved.

Incidentally, the wire connecting portions 14 and 25 are folded at rightangles with respect to the first electrode 1 and the second electrode 2and thus are in parallel with a side surface of the carriage arm 72.However, the wire connecting portions 14 and 25 may be used withoutbeing folded.

additionally, a head signal line is fixed onto the head suspension 74.Therefore, in the case that the head suspension 74 is connected to aground for the device, thus, to the actuator base 30, this embodimenthas an effect on noises against recording/reproducing signals for thehead. To realize this, a point X at the side of the base portion of thehead suspension 74 is connected to a point Y on the stationary portion33 of the actuator base 30, which is close to the point X, by aconductive piece or a lead wire (not shown). As a result, the headsuspension 74 is connected to the ground without wire routing andsoldering. Thus, an assembly operation is simplified.

If a conducting tongue 78 is formed by preliminarily expanding a part ofa relay FPC attaching portion at the side of the base portion of thehead suspension 74 to the actuator base 30 at that time as illustratedin FIG. 8C, the head suspension 74 is connected to the ground throughthe actuator base 30 simply by spot welding this conducting tongue 78 tothe actuator base 30 after-the mechanism 10 for producing a minutemovement of the head is assembled. Thus, the number of components isreduced. Consequently, the cost of the device is reduced still more.

Incidentally, in the first embodiment, the conductive layer 11 of thefirst electrode 1 is electrically insulated by the insulating layer 12thereof from the conductive layer 13 thereof. Moreover, the conductivelayer 11 of the second electrode 2 is insulated by the insulating layer12 thereof from the conductive layer 13 thereof. Thus, a ground fordriving the piezoelectric elements 31 is established separately from aground for the head signal. With such a structure, a voltage for drivingthe piezoelectric elements 31 hardly affects the S/N ratio of the headsignal.

FIG. 9A shows the constitution of an integrated electrode 8 which isintegrally constituted by the first electrode 1 and the second electrode2 to be used by the first embodiment. The integrated electrode 8 isformed by connecting a terminal portion at the side, at which the wireconnecting portion 14 is not provided, of the first electrode 1 toanother terminal portion at the side, at which the wire connectingportion 25 is not provided, of the second electrode 2 by a connectingwall 5 so that the conductive layers 11 are placed on the same side. Theintegrated electrode 8 is easily manufactured because the conductivelayers 11 are placed at the same side. Further, both end portions of theconnecting wall 5 of this integrated electrode 8, which are indicated byone-dot chain lines, are folded at a right angle so that both of the endportions thereof become valley portions. Furthermore, a border portion,which is indicated by a dashed line, between the wire connecting portion14 and the first electrode 1 and a border portion, which is indicated bya dashed line, between the wire connecting portion 25 and the secondelectrode 2 are folded at a right angle so that the border lines becomeridge portions. thus, the integrated electrode 8 is completed, asillustrated in FIG. 9B. It is sufficient that the piezoelectric elements31 are inserted between the first electrode 1 and the second electrode2.

Further, notches 6 may be provided in a part corresponding to a portionbetween the two piezoelectric elements 31 in each of the first electrode1 and the second electrode 2 of the integrated electrode 8, asillustrated in FIG. 9C. Owing to the notches 6, deformation of the hingeplate 40 is less limited by the electrodes 1 and 2. Thus, a large movingrange of the mechanism 10 is obtained. Furthermore, as illustrated inFIGS. 9D and 9E, the connecting wall 5 may be deleted after theintegrated electrode 8 shown in FIG. 9A is formed.

FIG. 10A is an exploded view showing the practical constitution of amechanism 10 for producing a minute movement of the head, which is thesecond embodiment of the present invention. FIG. 10B is a plan viewshowing the conditions of the mechanism 10 for producing a minutemovement of the head, which is shown in FIG. 10A, after assembled. FIG.10C is a side view of the mechanism 10 of FIG. 10B. The secondembodiment differs from the first embodiment only in that the secondembodiment has no means equivalent to the second electrode 2 of thefirst embodiment. Further, the second embodiment is an example in whichthe points X and Y of FIG. 8B showing the first embodiment are connectedby a conducting plate 7. Thus, in these figures showing the secondembodiment, the constituent elements of the second embodiment, which arethe same as the corresponding elements of the first embodiment, aredesignated by the same reference characters denoting the latter elementsof the first embodiment. Moreover, the description of such elements isomitted herein. Only the portions of the second embodiment, which differfrom the components of the first embodiment, will be describedhereinbelow.

A voltage is applied by the relay FPC 4 to the first electrode 1 and thesecond electrode 2 provided at both ends of the piezoelectric elements31 in the first embodiment, while the second electrode 2 is omitted andthus a voltage having a ground level is applied through the hinge plate40 to surfaces of the piezoelectric elements 31, which are at the sideof the hinge plate 40, in the second embodiment. Therefore, the hingeplate 40 is constituted by an electrical conductor and connected to theactuator base 30 through a conducting plate 7. The actuator base 30 iselectrically connected to the carriage arm 72 by caulking. The topsurfaces of the piezoelectric elements 31 are connected to the groundthrough the hinge plate 40, the conducting plate 7, the actuator base30, and the carriage arm 72. A voltage is applied to the bottom surfacesof the piezoelectric elements 31 through the first electrode 1.

Thus, the number of lead patterns in the relay FPC for driving thepiezoelectric elements 31 can be reduced by omitting the secondelectrode 2 and by using a common ground as both the ground for the headsuspension 74 and the ground for driving the piezoelectric elements 31.As a result of omitting the second electrode 2, the number ofcomponents, of the mechanism 10 for producing a minute movement of thehead is decreased. Moreover, the thickness and cost of the device arereduced.

FIG. 11A shows the practical constitution of a mechanism 10 forproducing a minute movement of a head, which is a modification of thesecond embodiment of the present invention illustrated in FIGS. 10A to10C. FIG. 11B is a plan diagram showing the mechanism of FIG. 10A afterit is assembled. This modification differs from the second embodimentonly in that the electrical connection between the hinge plate 40 andthe actuator base 30 is achieved by using the conducting tongue 78,which is provided by extending a part of the end portion of the relayFPC attaching portion 77 of the head suspension 74, instead of theconducting plate 7. The modification of the second embodiment is easilyrealized because the top surface of the hinge plate 40 and the topsurface of the actuator base 30 are flush with each other, as describedabove. Thus, constituent members of this modification, which are thesame as the corresponding components of the second embodiment, aredesignated by the same reference characters used to indicate the samecomponents of the second embodiment. Further, the description of suchconstituent members is omitted herein.

FIG. 12A is an assembling perspective diagram showing the practicalconstitution of another modification of the second embodiment of thepresent invention. This modification differs from the second embodimentand the former modification thereof described with reference to FIGS.10A, 10B, 11A, and 11B only in that the hinge plate 40 is connected tothe ground. Therefore, in these figures showing the latter modificationof the second embodiment, the constituent elements of this modification,which are the same as the corresponding elements of the secondembodiment and the former modification, are designated by the samereference characters denoting the latter elements of the secondembodiment and the former modification. Moreover, the description ofsuch elements is omitted herein. Only the portions of the secondembodiment, which differ from the components of the second embodimentand the former modification, will be described hereinbelow.

In the case of the latter modification of the second embodiment, a thirdelectrode 3 is mounted on the top surface of the hinge plate 40. Thisthird electrode 3 has the three-layer structure in which a conductive,layer 13, an insulating layer 12, and a conductive layer 11 are stackedfrom the side of the hinge plate 40 in this order. A wire connectingportion 15 projecting sideward from the end portion 35 of the actuatorbase 30 is provided in the third electrode 3. This wire connectingportion 15 is folded at a right angle along a side surface of thecarriage arm 72, so that the conductive layer 11 is exposed to theoutside. On the other hand, two penetration holes 16 are provided atpredetermined parts of the third electrode 3. Conductive adhesive agent18 is poured into these penetration holes 16, as illustrated in FIG.12B, after the third electrode 3 is mounted on the hinge plate 40. Theconductive layer 11 of the third electrode 3 is electrically connectedto the hinge plate 40 through this conductive adhesive agent 18.Further, the wire connecting portion 15 adjoins the wire connectingportion 14 of the first electrode 1 after the mechanism 10 for producinga minute movement of the head is assembled. Thus, the wire connectingportion 15 is connected to the ground by the relay FPC 4, similarly asthat in the case of the first embodiment.

Incidentally, the penetration holes 16 provided in the third electrode 3may be through holes 17 as illustrated in FIG. 12C. In this case, thehinge plate 40 and the third electrode 3 may be connected to each otherby solder instead of the conductive adhesive agent 17.

With such constitution, the force of the third electrode 3,whichprevents displacement of the hinge plate 40, is reduced. The movingrange of the mechanism 10 for producing a minute movement of the head isincreased. If a notch is similarly provided in the third electrode 3along the notch 41 of the hinge plate 40, the force for preventing thedeformation of the hinge plate 40 is efficiently reduced still more.

FIG. 13A is an exploded view showing the practical constitution of themechanism 10 for producing a minute movement of the head, which is thethird embodiment of the present invention. FIG. 13B is a plan viewshowing the condition of the mechanism 10 for producing a minutemovement of the head, which is shown in FIG. 13A, after assembled. FIG.13C is a side view of the mechanism 10 of FIG. 13B. The third embodimentdiffers from the first embodiment only in that the third embodiment hasno means equivalent to the first electrode 1 of the first embodiment.Further, the third embodiment is an example in which the points X and Yof FIG. 8B showing the first embodiment are connected by a conductingplate 7. Thus, in these figures showing the third embodiment, theconstituent elements of the third embodiment, which are the same as thecorresponding elements of the first embodiment, are designated by thesame reference characters denoting the latter elements of the firstembodiment. Moreover, the description of such elements is omittedherein. Only the portions of the third embodiment, which differ from thecomponents of the first embodiment, will be described hereinbelow.

A voltage is applied by the relay FPC 4 to the first electrode 1 and thesecond electrode 2 provided at both ends of the piezoelectric elements31 in the first embodiment, while the first electrode 1 is omitted andthus a voltage having a ground level is applied to surfaces of thepiezoelectric elements 31, which are at the side of the actuator base30, through the actuator base 30 in the third embodiment. That is, thesurfaces, which are at the side of the actuator base 30, of thepiezoelectric elements 31 are connected to the ground by the conductiveactuator base 30, which is connected through the, caulking projections32, to the carriage arm 72 connected to the ground. Further, a voltageis applied to the surfaces, which are at the side of the hinge plate 40,of the piezoelectric elements 31 through the second electrode 2 havingthe wire connecting portion 25 provided on a side surface thereof.Furthermore, the head suspension 74 is connected to the hinge plate 40that is connected to the ground through the conducting plate 7, theactuator base 30, and the carriage arm 72.

FIGS. 14A to 14C show the practical constitution of a mechanism forproducing a minute movement of a head, which is a modification of thethird embodiment of the present invention illustrated in FIGS. 13A to13C. FIG. 14A is an assembly diagram showing this modification. FIG. 14Bis a plan view showing this modification after it is assembled. FIG. 14Cis a side view of this modification of FIG. 14B. This modificationdiffers from the third embodiment only in that the electrical connectionbetween the hinge plate 40 and the actuator base 30 is achieved by usingthe conducting tongue 78, which is provided by extending a part of theend portion of the relay FPC attaching portion 77 of the head suspension7!4, instead of the conducting plate 7. Thus, constituent members ofthis modification, which are the same as the corresponding components ofthe third embodiment, are designated by the same reference charactersused to indicate the same components of the third embodiment. Further,the description of such constituent members is omitted herein.

FIG. 15A is an exploded diagram showing the practical constitution of amechanism 10 for producing a minute movement of a head, which is afourth embodiment of the present invention. FIG. 15B is an enlarged viewof the head suspension 74 and the hinge plate 40 of FIG. 15A. The fourthembodiment differs from the first embodiment only in a method ofconnecting the head suspension 74 and the hinge plate 40 of the firstembodiment to the ground. Therefore, in these figures showing the fourthembodiment, the constituent elements of this embodiment, which are thesame as the corresponding elements of the first embodiment, aredesignated by the same reference characters denoting the latter elementsof the first embodiment. Moreover, the description of such elements isomitted herein. Only the portions of the fourth embodiment, which differfrom the components of the first embodiment, will be describedhereinbelow.

In the case of the first embodiment, the head suspension 74 and thehinge plate 40 are connected to the ground by the following method. Thatis, as illustrated in FIGS. 8B and 8C, the point X is connected to thepoint Y by the conducting plate 7. Alternatively, the head suspension 74is connected to the actuator base 30 by a conducting tongue 78 providedin the relay FPC attaching portion 77 of the head suspension 74.Different to this, in the case of the fourth embodiment, a groundingterminal 81 is provided at the relay FPC attaching portion 77 of thehead suspension 74, in addition to a relay terminal 79 of a lead pattern69 connected to the head.

Therefore, in the case of the fourth embodiment, the head suspension 74is connected to the ground by the relay FPC (not shown) to be connectedto this grounding terminal 81. Further, in the fourth embodiment, thehinge plate 40 is connected to the ground by connecting this groundingterminal 81 to the hinge plate 40 by a conducting plate 47, as shown inFIG. 15B. Similarly as in the case of the first embodiment, a voltage isapplied to the piezoelectric elements 31 through the first electrode 1and the second electrode 2 in the fourth embodiment.

Next, the mechanism of the present invention for producing a minutemovement of the head, which is constituted in the second mode, will bedescribed, based on fifth to seventh embodiments of the presentinvention.

FIG. 16 shows the constitution of the mechanism 10 for producing aminute movement of the head, which is the fifth embodiment of thepresent invention. In the fifth embodiment, a stationary portion 33 ofan actuator base 20 formed like a plate is fixed to the carriage arm 72by a caulking projection 32. The carriage arm 72 is usually connected tothe ground. On the other hand, a portion, which is at the side of a baseportion 43 of a movement-amount increasing portion 44, of a hinge plate50 is folded twice like a crank. Further, a step portion 46 is formedbetween the movement-amount increasing portion 44 and a second notch 42.At that time, the hinge plate 50 is folded so that the movement-amountincreasing portion 44 and the base portion 43 are in parallel with eachother.

The base portion 43, on which the piezoelectric elements 31 put betweenthe first electrode 1 and the second electrode 2, of the hinge plate 50is connected to the bottom surface of the end portion 35 of the actuatorbase 20. Similarly as in the case of the mechanism constituted in thefirst mode, each of the first electrode 1 and the second electrode 2consists of a conductive layer 11 constituted by an electricalconductor, such as copper, an insulating layer 12 constituted by anelectrical insulator, such as polyimide, and a conductive layer 13constituted by an electrical conductor, such as SUS, which are stackedfrom the side of the piezoelectric elements 31 in this order.

At that time, the top surfaces of the actuator base 20 and the hingeplate 50 are trued up and made to be flush with each other by settingthe height of the step portion 46 of the actuator base 20 at apredetermined height. Thus, the top surfaces of the actuator base 20 andthe hinge plate 50 are trued up and flush with each other. In the caseof the mechanism constituted in the second mode, the distance betweenthe base portion 43 of the hinge plate 50 and the head can be set at alarge value, in comparison with the case of the mechanism constituted inthe first mode. Thus, the former mechanism has an advantage in that thedisplacement increasing ratio of the hinge plate 50 is set at a largevalue.

FIG. 17 shows the practical constitution of the fifth embodiment of thepresent invention. The stationary portion 33 of the plate-like actuatorbase 20 is inserted, as a caulking projection 32, into a caulking hole72 a bored in the carriage arm 72 and then caulked and fixed thereto.The carriage arm 72 is connected to the ground. Moreover, the hingeplate 50 has base portions 43 and a movement-amount increasing portion44 partitioned by a first notch 41 and second notches 42. A part, whichis close to the second notch 42, of the movement-amount increasingportion 44 is folded twice and formed as a step portion 46. The baseportions 43 of the hinge plate 50 are placed in such a manner as to bein parallel with the movement-amount increasing portion 44 and to belower than the portion 44 by a height of one step. Furthermore, the headsuspension 74 is fixed to the movement-amount increasing portion 44 ofthe hinge plate 50 by spot welding. Incidentally, reference numeral 77denotes a relay-FPC attaching portion provided in a base-portion-sidesurface of the head suspension 74.

The piezoelectric elements 31 put between the first electrode 1 and thesecond electrode 2 are mounted on the base portion 43. Each of the firstelectrode 1 and the second electrode 2 has the three-layer structuredescribed by referring to FIG. 16. Each of the conductive layers 11 isplaced at a side that is in contact with the piezoelectric elements, 31.The fifth embodiment is similar to the mechanism constituted in thefirst mode in that a wire connecting portion 14 is provided in the firstelectrode 1 and that a wire connecting portion 25 is provided in thesecond electrode 2. The piezoelectric elements 31 put between the firstelectrode 1 and second electrode 2 are the same as the elements 31described with reference to FIG. 2. The directions of polarization ofthe piezoelectric elements 31 are perpendicular to the direction ofthickness of these elements and opposite to each other.

FIG. 18A is a side diagram showing the mechanism 10 for producing aminute movement of a head, which is the fifth embodiment of the presentinvention illustrated in FIG. 17A, after assembled. FIG. 18B is a planview of the assembled mechanism 10 for producing a minute movement ofthe head. As illustrated in FIG. 18A, when the mechanism 10 forproducing a minute movement of the head is assembled, the first wireconnecting portion 14 and the second wire connecting portion 25respectively provided on the bottom and top surfaces of thepiezoelectric elements 31 are placed in such a way as to be adjacent toeach other. This facilitates soldering of the relay FPC in which leadpatterns for the wire connecting portions 14 and 25 are formed.Consequently, the applying of a voltage to each of the first electrode 1and the second electrode 2 is easily achieved by soldering the relay FPCin which lead patterns 48 and 49 for the wire connecting portions 14 and25 are formed.

Incidentally, a head signal line is fixed onto the head suspension 74.Therefore, in the case that the head suspension 74 is connected to aground for the device and, thus, to the actuator base 30, thisembodiment has an effect on noise effecting recording/reproducingsignals to and from the head. To realize this, a point X at the side ofthe base portion of the head suspension 74 is connected to a point Y onthe stationary portion 33 of the actuator base 20, which is close to thepoint X, by a conductive piece or a lead wire (not shown). If aconducting tongue 78 is formed by preliminarily expanding a part of arelay FPC attaching portion at the side of the base portion of the headsuspension 74 to the actuator base 20 at that time as illustrated inFIG. 18C, the head suspension 74 is connected to the ground through theactuator base 20 simply by spot welding this conducting tongue 78 to theactuator base 20 after the mechanism 10 for producing a minute movementof the head is assembled. Furthermore, the electrodes described withreference to FIGS. 9A to 9E may be used as the first electrode 1 and thesecond electrode 2.

FIG. 19A is an exploded view showing the practical constitution of amechanism 10 for producing a minute movement of the head which is thesixth embodiment of the present invention. The sixth embodimentcorresponds to the second embodiment of the mechanism 10 for producing aminute movement of the head, which is constituted in the first mode.That is, the sixth embodiment corresponds to the constitution obtainedby removing the electrode provided at the side of the hinge plate 40from the first embodiment. Therefore, the sixth embodiment differs fromthe fifth embodiment only in that the sixth embodiment has no meansequivalent to the electrode, which is placed at the side of the hingeplate 50, of the fifth embodiment, namely, to the first electrode 1, andin that the second electrode 2 having a wire connecting portion 27,whose position is changed, of the sixth embodiment differs in shape fromthe second electrode 2 of the fifth embodiment. Further, the sixthembodiment is an example in which the points X and Z of FIG. 18B showingthe fifth embodiment are connected by a conducting plate 7. Thus, inthese figures showing the sixth embodiment, the constituent elements ofthe sixth embodiment, which are the same as the corresponding elementsof the fifth embodiment, are designated by the same reference charactersdenoting the latter elements of the fifth embodiment. Moreover, thedescription of such elements is omitted herein. Only the portions of thesecond embodiment, which differ from the components of the fifthembodiment, will be described hereinbelow.

A voltage is applied by the relay FPC 4 to the first electrode 1 and thesecond electrode 2 provided at both ends of the piezoelectric elements31 in the fifth embodiment, while the first electrode 1 is omitted andthus a voltage having a ground level is applied through the hinge plate50 to surfaces of the piezoelectric elements 31, which are at the sideof the hinge plate 50, in the sixth embodiment. Therefore, the hingeplate 50 is constituted by an electrical conductor. The head suspension74 electrically connected to the hinge plate 50 by spot welding isconnected to the actuator base 20 by using a conducting plate 7. Theactuator base 20 is electrically connected to the carriage arm 72 bycaulking. The bottom surfaces of the piezoelectric elements 31 areconnected to the ground through the hinge plate 50, the conducting plate74, the actuator base 20, and the carriage arm 72. A voltage is appliedto the top surfaces of the piezoelectric elements 31 through the secondelectrode 2.

FIG. 19B is an exploded view showing the practical constitution, of amechanism 10 for producing a minute movement of a head which is amodification of the sixth embodiment of the present invention. Thismodification differs from the sixth embodiment only in that theelectrical connection between the head suspension 74 and the actuatorbase 20 is achieved by using the conducting tongue 78, which is providedby extending a part of the end portion of the relay FPC attachingportion 77 of the head suspension 74, instead of the conducting plate 7.Thus, constituent members of this modification, which are the same asthe corresponding components of the sixth embodiment, are designated bythe same reference characters used to indicate the same components ofthe sixth embodiment. Further, the description of such constituentmembers is omitted herein.

FIG. 20 is an exploded view showing the practical constitution ofanother modification of the sixth embodiment of the present invention.This modification corresponds to the latter modification of the secondembodiment, which is the mechanism constituted in the first modeillustrate in FIGS. 12A to 12C. This modification of the sixthembodiment differs from the sixth embodiment and the former modificationthereof described with reference to FIGS. 19A and 19B only in that thehinge plate 50 is connected to the ground. Therefore, in these figuresshowing the latter modification of the sixth embodiment, the constituentelements of this modification, which are the same as the correspondingelements of the sixth embodiment and the former modification, aredesignated by the same reference characters denoting the latter elementsof the sixth embodiment and the former modification. Moreover, thedescription of such elements is omitted herein. Only the portions of thelatter modification of the sixth embodiment, which differ from thecomponents of the sixth embodiment and the former modification thereof,will be described hereinbelow.

In the case of the latter modification of the sixth embodiment, a thirdelectrode 3 having a three-layer structure is mounted on the bottomsurface of the hinge plate 50. A wire connecting portion 15, whichprojects sideward from the end portion 35 of the actuator base 20 and isprovided in the third electrode 3, is folded at a right angle along aside surface of the carriage arm 72, so that the conductive layer 11 isexposed to the outside. As described with reference to FIGS. 12A to 12C,two penetration holes 16 or through holes 17 are provided atpredetermined parts of the third electrode 3. The third electrode 3 iselectrically connected to the hinge plate 50 by using conductiveadhesive agent 18 or solder. Further, the wire connecting portion 15adjoins the wire connecting portion 27 of the second electrode 2′ afterthe mechanism 10 for producing a minute movement of the head isassembled. Thus, the wire connecting portion 15 is connected to theground by the relay FPC 4, similar to that in the case of the fifthembodiment.

FIG. 21A is an exploded view showing the practical constitution of themechanism 10 for producing a minute movement of the head which is theseventh embodiment of the present invention. The seventh embodimentdiffers from the fifth embodiment only in that the seventh embodimenthas no means equivalent to the second electrode 2′ of the fifthembodiment. Further, the seventh embodiment is an example in which thepoints X and Z of FIG. 18B showing the fifth embodiment are connected bya conducting plate 7. Thus, in these figures showing the seventhembodiment, the constituent elements of the seventh embodiment, whichare the same as the corresponding elements of the fifth embodiment, aredesignated by the same reference characters denoting the latter elementsof the fifth embodiment. Moreover, the description of such elements isomitted herein. Only the portions of the seventh embodiment, whichdiffer from the components of the fifth embodiment, will be describedhereinbelow.

A voltage is applied by the relay FPC 4 to the first electrode 1 and thesecond electrode 2 provided at both ends of the piezoelectric elements31 in the fifth embodiment, while the second electrode 2′ is omitted andthus a voltage having a ground level is applied to surfaces of thepiezoelectric elements 31, which are at the side of the actuator base20, through the actuator base 30 in the seventh embodiment. That is, thesurfaces, which are at the side of the actuator base 30, of thepiezoelectric elements 31 are connected to the ground by the conductiveactuator base 20, which is connected through the caulking projections32, to the carriage arm 72 connected to the ground. On the other hand, avoltage is applied to the surfaces, which are at the side of the hingeplate 50, of the piezoelectric elements 31 through the first electrode 1having the wire connecting portion 14 provided on a side surfacethereof. Furthermore, the hinge plate 50 is connected to the headsuspension 74 that is connected to the ground through the conductingplate 7 and the actuator base 20.

FIG. 21B shows the practical constitution of a mechanism 10 forproducing a minute movement of a head, which is a modification of theseventh embodiment of the present invention. This modification differsfrom the seventh embodiment only in that the electrical connectionbetween the head suspension 74 and the actuator base 20 is achieved byusing the conducting tongue 78, which is provided by extending a part ofthe end portion of the relay FPC attaching portion 77 of the headsuspension 74, instead of the conducting plate 7. Thus, constituentmembers of this modification, which are the same as the correspondingcomponents of the seventh embodiment, are designated by the samereference characters used to indicate the same components of the seventhembodiment. Further, the description of such constituent members isomitted herein.

As described above, in the case of the mechanism 10 of the presentinvention for producing a minute movement of the head,a height H from adisk-medium-side surface of the slider 71 to a surface, which is at theside opposite to the disk medium, of the carriage arm 72 is reduced.Moreover, the energizing of the electrodes placed on the top and bottomsurfaces of the piezoelectric elements 31 is easily achieved through thewire connecting portions. Hereunder, the difference in the heightbetween the conventional mechanism for producing a minute movement ofthe head and the mechanism of the present invention for producing aminute movement of the head will be described by using FIGS. 22A and22B.

FIG. 22A schematically shows the constitution of the conventionalmechanism 70 for producing a minute movement of the head, which has beendescribed with reference to FIGS. 1 to 3B. In the conventional mechanism70 for producing a minute movement of the head, the actuator base ismounted on the carriage arm. Further, the hinge plate is mounted on thisactuator base by putting the piezoelectric elements therebetween.Moreover, the head suspension having the slider is fixed to this hingeplate. Let h1, h2, h3, h4, h5, and h6 denote a thickness of the slider,a thickness of the head suspension, a thickness of the hinge plate, athickness of the piezoelectric elements, a thickness of the actuatorbase, and a thickness of the carriage arm, respectively. Thus, theheight H from the disk-medium-side surface of the slider 71 to thesurface, which is at the side opposite to the disk medium, of thecarriage arm 72 is given by the following equation:

H=h 1+h 2+h 3+h 4+h 5+h 6

In contrast with this, in the case of the mechanism 10 of the presentinvention for producing a minute movement of the head, which isconstituted in the first mode, the actuator base, which is folded like acrank and has a lowered end portion, is mounted on the carriage arm.Further, the hinge plate is mounted on the portion, which is lowered bythe height of one step, of this actuator base by putting thepiezoelectric elements therebetween. Furthermore, the head suspensionhaving the slider is fixed to this hinge plate. Incidentally, supposingthat the actuator base is folded so that the top surface of the hingeplate and the top surface of the actuator base are at the same positionor level, the height H from the disk-medium-side surface of the slider71 to the surface, which is at the side opposite to the disk medium, ofthe carriage arm 72 is given by the following equation where thethickness of the slider, the thickness of the head suspension, thethickness of the hinge plate, the thickness of the piezoelectricelements, the thickness of the actuator base, and the thickness of thecarriage arm are denoted by h1, h2, h3, h4, h5, and h6, respectively.Additionally, this height H has the same value even in the secondembodiment of the present invention in which a step is provided at theside of the hinge plate.

H=h 1+h 2+h 3+h 6

Thus, according to the present invention, the thickness of thepiezoelectric elements including the electrodes and the thickness of oneof the hinge plate and the actuator base are decreased by containingsuch constituent elements in a front portion of the carriage arm, whichis originally thick. Consequently, the height of the head actuator ofthe present invention for accessing disk media of the same number, thatis, the height of the disk device, is decreased.

Further, the constitution of the wire connecting portion 14 of the firstelectrode 1 of the present invention and that of the wire connectingportion 25 of the second electrode 2 may be applied to the conventionalmechanism 70 for producing a minute movement of the head. FIG. 23 showsan embodiment of the present invention, in which the first electrode 1and the second electrode 2 are employed as the electrodes for thepiezoelectric elements 31 of the conventional mechanism 70 for producinga minute movement of the head, which has been described by referring toFIG. 2A. The need for forming the wiring patterns 21 and 22 on thecarriage arm 72 is eliminated by adopting the first electrode 1 and thesecond electrode 2 of the present invention. Electric power is fed tothe piezoelectric elements by the relay FPC. Thus, the constitution ofthe mechanism 70 for producing a minute movement of the head issimplified.

Thus, in the case of the mechanism for producing a minute movement ofthe head according to the present invention, which uses thepiezoelectric elements utilizing shear deformation thereof, thethickness of this mechanism is reduced. Consequently, the presentinvention has an effect in that the height of the head actuator islimited to a low value and that the thickness of the disk device isreduced. Moreover, the wiring for driving the piezoelectric elements issimplified by providing protruded wire connecting portions in the sidesurfaces of the carriage arm. Consequently, the cost of the device isreduced.

Although the preferred embodiments of the present invention have beendescribed above, it should be understood that the present invention isnot limited thereto and that other modifications will be apparent tothose skilled in the art without departing from the spirit of theinvention.

The scope of the present invention, therefore, should be determinedsolely by the appended claims.

What is claimed is:
 1. A mechanism for producing a minute movement of ahead, provided between a base portion of a head suspension having thehead at an end portion thereof, and an end portion of a carriage armswinging around a rotation shaft in a rocking type head actuator, saidmechanism comprising: a stationary member, fixed to said end portion ofsaid carriage arm; a moving member, attached to said base portion ofsaid head suspension; and a displacing member, interposed between apredetermined surface area of a tip portion of said stationary memberand a predetermined surface area of said moving member opposed to saidstationary member, having a top surface to be displaced with respect toa bottom surface thereof by applying a voltage in a direction ofthickness thereof, wherein said displacing member is interposed betweena free-end of said stationary member and an end of said moving memberadjacent said carriage-arm, so as to position said displacing member ina dead space delineated generally by the thickness of said carriage arm,to which said base portion of said head suspension is attached.
 2. Themechanism for producing a minute movement of a head according to claim1, wherein a space is formed between a free-end of said stationarymember and a free-end of said moving member by folding said stationarymember in a direction of the thickness of said carriage arm like acrank, and wherein said displacing member is accommodated in said space.3. The mechanism for producing a minute movement of a head according toclaim 1, wherein a space is formed between the free-end of saidstationary member and a free end of said moving member by folding saidmoving member in a direction of the thickness of said carriage arm likea crank, and wherein said displacing member is accommodated in saidspace.
 4. The mechanism for producing a minute movement of a headaccording to claim 1, wherein application of the voltage to saiddisplacing member is performed by sheet-like electrode members providedon the top and bottom surfaces of said displacing member, whereininsulating members are interposed between said electrode member and saidstationary member and between said electrode member and said movingmember, and wherein each of said electrode members has a wire connectingportion connected to external wiring that is connected to a powersupply.
 5. The mechanism for producing minute movement of a headaccording to claim 4, wherein said electrode member is constituted bystacking a stainless-steel thin plate, a polyimide layer, and a copperfoil in this order.
 6. The mechanism for producing minute movement of ahead according to claim 4, wherein said electrode member is constitutedby a flexible printed circuit board and the connection of the printedcircuit board, the piezoelectric element, the moving member, and thestationary member is performed by gluing.
 7. The mechanism for producingminute movement of a head according to claim 4, wherein said wireconnecting portion of the electrode member is folded in such a way as tofit along a side surface of the carriage arm.
 8. The mechanism forproducing a minute movement of a head according to claim 1, wherein saidcarriage arm is connected to the ground, wherein said stationary memberincludes an electrical conductor fixed in electrical contact to said endportion of said carriage arm, wherein an insulating layer, a conductivelayer, and an electrode member having a wire connecting portionconnected to external wiring, which is connected to a power supply, areprovided between said stationary member and said displacing member sothat said conductive layer is provided at a side of said displacingmember, wherein said moving member is constituted by an electricalconductor and attached to said base portion of said head suspension insuch a way as to electrically conduct, and wherein said moving member isconnected to said stationary member by an electrical conductor.
 9. Themechanism for producing a minute movement of a head according to claim1, wherein said carriage arm is connected to the ground, wherein saidstationary member includes an electrical conductor fixed in electricalcontact to said end portion of said carriage arm, wherein an insulatinglayer, a conductive layer, and an electrode member having a wireconnecting portion connected to external wiring, which is connected to apower supply, are provided between said stationary member and saiddisplacing member so that said conductive layer is provided at a side ofsaid displacing member, wherein said moving member includes anelectrical conductor attached to said base portion of said headsuspension in such a way as to electrically conduct, overlaid directlyon said displacing member, and wherein said moving member is connectedto said stationary member by an electrical conductor.
 10. The mechanismfor producing minute movement of a head according to claim 9, whereinsaid electrical conductor is a part of said head suspension.
 11. Themechanism for producing a minute movement of a head according to claim1, wherein said moving member includes an electrical conductor, whereinan electrode member consisting of an insulating layer and an electricalconductive layer is fixed to a selected surface of said moving member,which is opposite to said displacing member, wherein said electrodemember has a wire connecting portion connected to external wiring, andwherein said conductive layer of said electrode member is connected tosaid moving member by an electrical conductor.
 12. The mechanism forproducing minute movement of a head according to claim 11, wherein saidelectrical conductor is a conductive adhesive agent.
 13. The mechanismfor producing a minute movement of a head according to claim 1, whereinsaid carriage arm is connected to the ground, wherein an electrodemember consisting of an insulating layer, an electrical conductivelayer, and a connecting terminal portion to be connected to an externallead wire is provided so that said conductive layer is in contact with asurface of said displacing member adjacent the moving member, wherein asurface of said displacing member adjacent the stationary member iselectrically connected to said carriage arm through said stationarymember by an electrical conductor, and wherein said moving member, towhich said head suspension is attached, includes an electrical conductorconnected to said stationary member.
 14. The mechanism for producing aminute movement of a head according to claim 1, wherein said carriagearm is connected to the ground, wherein an electrode member consistingof an insulating layer, an electrical conductive layer, and a connectingterminal portion to be connected to an external lead wire is provided sothat said conductive layer is in contact with a surface of saiddisplacing member adjacent the moving member, wherein a surface of saiddisplacing member adjacent the stationary member is electricallyconnected to said carriage arm through said stationary member, whereinsaid moving member includes an electrical conductor connected to saidbase portion of said head suspension in such a way as to electricallyconduct, and is overlaid directly on said displacing member, and whereinsaid head suspension is connected to said stationary member by anelectrical conductor.
 15. The mechanism for producing minute movement ofa head according to claim 4, wherein said moving member has a hingeportion for increasing a moving range of the head suspension, and saidelectrode member has a notch that complements a shape of said hinge ofsaid moving member.
 16. The mechanism for producing minute movement of ahead according to claim 1, wherein a surface of said head suspension onwhich said moving member is mounted is flush with an outer surface ofsaid stationary member opposite to an inner surface which is mounted onthe carriage arm.
 17. A mechanism for producing a minute movement of ahead, provided between a base portion of a head suspension having thehead at an end portion and an end portion of a carriage arm swingingaround a rotation shaft in a rocking type head actuator, said mechanismcomprising: a stationary member, fixed to said end portion of saidcarriage arm; a moving member, attached to said base portion of saidhead suspension; a displacing member, interposed between a predeterminedsurface area in a tip portion of said stationary member and a surface ofsaid moving member opposed to said stationary member, having a topsurface to be displaced with respect to a bottom surface thereof byapplying a voltage in a direction of thickness thereof; and a sheet-likeelectrode member, disposed on at least one of top and bottom surfaces ofsaid displacing member, having an insulating layer and conductivelayers, wherein said electrode member has a wire connecting portionconnected to external wiring, and wherein said wire connecting portionis folded in such a way as to be along a side surface of said carriagearm.